Humber cars, who produced important vehicles in WW2, armoured cars and famously Montgomery's staff car, were manufacturing in Beeston near Chilwell in WW1 and so its workers would have heard the tragic explosion at the then Shell Filling Factory on 1 July 1918. The Chilwell site became the Army Centre for Mechanisation in WW2, as I describe in War on Wheels.
Holt tractors, helped by patents sold by Hornsby in Grantham and manufactured in the UK by Rustons of Lincoln, became Caterpillar because 'they looked like a giant caterpillar crossing the ground'. Holt caterpillar tractors were used to haul heavy artillery in WW1.
Herbert Austin was the driving force behind Wolseley which became part of the Morris, or Nuffield, group of companies. Neither Austin nor Morris were great vehicle producers in WW1, but both contributed greatly to the war effort in other armaments.
Daimler produced the engine for the first tanks and also for their own and AEC's 3 ton trucks.